[petsc-users] =?gb2312?Q?RE:_[petsc?= =?gb2312?Q?-users]_Ho?= =?gb2312?Q?w_to_imple?= =?gb2312?Q?ment_press?= =?gb2312?Q?ure_convec?= =?gb2312?B?dGlvbqhDZGlmZnU=?= =?gb2312?Q?sion_preco?= =?gb2312?Q?nditioner_?= =?gb2312?Q?in_petsz?=

[keguoyi]

Dear Matthew,

Thanks for the last Email. For the LSC preconditioner in Petsc, it allows to do inv(S)= inv(A10 A01) A10 A00 A01 inv(A10 A01). Is it also possible to do inv(S)= inv(Mp) Fp inv(Ap), where Mp and Ap are built by ourselves and not the same matrices. Thanks a lot.

Best,
Guoyi

Date: Mon, 12 Oct 2015 08:46:35 -0500
Subject: Re: [petsc-users] How to implement pressure convection¨Cdiffusion preconditioner in petsz
From: knepley at gmail.com
To: coyigg at hotmail.com
CC: petsc-users at mcs.anl.gov

On Mon, Oct 12, 2015 at 1:49 AM, keguoyi <coyigg at hotmail.com> wrote:



Dear Petsc developers and users,  

This is Guoyi ke, a graduate student in Texas Tech University.  I have a 2D Navier Stokes problem that has block matrices: J=[F    B^T; B    0]. I want to build a pressure convection¨Cdiffusion preconditioner (PCD) P=[F    B^T; 0   Sp]. Here, we let Sp=-Ap(Fp)^(-1)Mp approximate schur complement S=-BF^(-1)B^T, where Ap is pressure Laplacian matrix, Mp is pressure mass matrix, and Fp is convection-diffusion operators on pressure space.

 We use right preconditioner J*P^(-1)=[F    B^T; B    0] * [F    B^T; 0    Sp]^(-1), and is it possible for Petsz to build and implement this precondioner P? Since (Sp)^(-1)=-(Mp)^(-1) Fp(Ap)^(-1), is it possible that we can solve (Mp)^(-1) and (Ap)^(-1) by CG method separately inside preconditioner P. 

Take a look at the PCFIELDSPLIT preconditioner. I think you want the LSC option for that (http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCLSC.html)if I am reading your mail correctly.
  Thanks,
    Matt Any suggestion will be highly appreciated. Thank you so much!

Best,
Guoyi 
 		 	   		  


-- 
What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener
 		 	   		  
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